Links and Further Reading

https://airnow.gov

Air Now offers clear explanations of EPA air quality standards.

https://purpleair.com

Purple Air provides low-cost particulate matter sensors.

https://megacities.jpl.nasa.gov/portal

The Megacities Carbon Project measures atmospheric trends. 

https://www.lung.org

The American Lung Association publishes The State of the Air Report, yearly.

https://openaq.org

Provides air quality data for cities around the world.

https://www.globalchange.gov

 Published the Fourth National Climate Assessment.